St Mary’s is the cathedral church of the Roman Catholic Diocese of Ossory. It is situated on James’s Street, Kilkenny, Ireland.
Saint Mary’s was designed by William Deane Butler (c.1794-1857). He was chosen by Bishop William Kinsella (1793-1845) who instigated the building of St. Mary’s in February 1842. Work began in April 1843 and finished in 1857. On Sunday 4 October 1857, St. Mary’s had its grand opening, which consisted of a two-and-three-quarter hour ceremony that began at 6.15am. The cost of the building is estimated to have been £25,000.